Reducing tube-wall eccentricity in tube intermediates

ABSTRACT

A method of correcting eccentricity in the inner and outer circumferential surfaces bounding a tube wall. First high and low wall thickness regions are determined. Material then is removed from the regions of high wall thickness. Subsequently the tube wall is worked, to remove ovality in the cross section introduced by the material removal, thus to reintroduce roundness to the tube.

United States Patent Baksay 1 [54] REDUCING TUBE-WALL ECCENTRICITY IN TUBE INTERMEDIATES [72] Inventor: Ivan Baksay, 1113 West 29th Street, Albany, Oreg. 97321 221 Filed: May17,1971

211 Appl.No.: 143,830

[52] US. Cl. ..72/341, 72/367, 51/290 [51] Int. Cl ..B2lc 37/30 [58] Field of Search ..72/324, 340, 341, 367; 29/424;

[56] References Cited UNITED STATES PATENTS Briney ..72/340 [4 1 Oct. 17,1972

2,047,055 7/1936 Blood ..51/290 2,819,629 l/l958 Robinson ..72/341 3,095,083 6/1963 Hglble et 1 ..72/367 Primary Examiner-Lowell A. Larson Attorney-Kolisch, Hartwell & Dickinson [57] ABSTRACT A method of correcting eccentricity in the inner and outer circumferential surfaces bounding a tube wall. First high and low wall thickness regions are determined. Material then is removed from the regions of high wall thickness. Subsequently the tube wall is worked, to remove ovality in the cross section introduced by the material removal, thus to reintroduce roundness to the tube.

3 Claims, 2 Djawing Figures REDUCING TUBE-WALL ECCENTRICITY IN TUBE INTERMEDIATES This application is a continuation-in-part of copending application Ser. No. 18,387, filed Feb. 26, 1970.

This invention relates to the manufacture of a tube or tubing, and more particularly to a method of making such tubing wherein eccentricity in the inner and outer circumferential surfaces is corrected.

In the manufacture of a tube from a tube of larger diameter and greater wall thickness, the latter sometimes being referred to as a tube hollow or an intermediate, it is common to work the tube walls as by swaging, drawing, tube reducing, etc. It has been found, however, that where a tube hollow or intermediate has eccentric inner and outer surfaces, such working of the tube wall improves the eccentricity only to a small extent.

Tube hollows or intermediates with total eccentricities of up to 20 percent of the wall thickness in the tube mayyield final tube products that meet final product specifications. However, if permissible wall tolerance is used up substantially or completely by this eccentricity, there is little if any tolerance left to absorb other deviations. With the probability that final product specifications will not be met with tubing of say 20 percent eccentricity, the manufacturer is forced with the necessity of scrapping a product rather than to perform expensive manufacturing steps on the tube hollow only to find ultimately that specifications are not met.

Generally, this invention concerns a method of processing tubing, such as tube hollows or intermediates, enabling correction of eccentricity in inner and outer surfaces of the tubing.

One result of practicing the method is a sharp reduction in starting material that need be scrapped where critical specifications must be adhered to in the final tubing product.

Another object of the invention comprises the provision of a method for correcting such eccentricity in tube wall surfaces, which comprises removing material in thick regions of a tube wall once such have been located, and then working the tube wall to remove ovality introduced therein by such material removal.

The method contemplated may be practiced with such material removal performed on either the inner or outer circumference of the tube. In either instance a final product is obtainable capable of meeting critical specifications using starting products that otherwise would have to be scrapped.

These and other objects and advantages are attained by the invention, illustrated in the accompanying drawings wherein:

FIG. 1 is a cross section of a tube hollow having eccentric inner and outer circumferential surfaces, and indicating diagrammatically how such may be corrected using the processes of the invention with material removal on the inner circumference of the tube hollow; and

FIG. 2 further illustrates the invention in connection with a tube hollow having eccentric inner and outer circumferences with material removal performed on the outer circumference of the tube.

The invention will be described herein in connection with the manufacture of cladding for nuclear reactors. In this instance it is common to utilize as such cladding tubing made from zirconium base alloys, having a final outer diameter or CD. which typically: may be about 0.5 inch. In the manufacture of such tubing it is common to start with a tube hollow of, for example, 2.5 inches O.D., and a wall thickness of, for example, 0.350 inch. Such a tube hollow is passed. in successivepasses through a tube reducer, with tube wall area reduction taking place in each pass, to reduce the diameter and tube wall thickness, whereby the final product is obtained.

Tubing for cladding as well as tubing utilized in other applications must meet critical specifications with regard to wall tolerances. As a consequence, it is in this type of manufacture that the method of the invention has particular advantages.

Generally describing the process contemplated, initially the high and low wall thickness regions in the tube hollow are determined. In the ordinary instance the zones of maximum and minimum wall thickness are substantially directly across from each other in the tube. With an extruded tube the zone of maximum wall thickness, as well as the zone of minimum thickness, extends substantially longitudinally of the tube, although it is recognized that with a tube hollow prepared by other types of processes this relationship may not always exist.

Having determined the high and low wall regions or zones in the tube, which may be done ultrasonically, or using other well-known means, the tube is processed to remove material from the high wall region. This removal of material is selective, in that the material is. not removed from the low wall region. The material removal may be done by blasting or abrading, etc., utilizing conventional procedures.

In FIG. 1 I have illustrated the invention as practiced on a tube with eccentric inner and outer circumferences wherein the material removal is performed on the inner circumference of the tube.

The tube shown at 10 in FIG. 1 includes a region of high wall thickness indicated generally at 10a, and a region of low wall thickness indicated at 10b. It should be understood that these regions have been greatly overemphasized in the drawings for purposes of illustration.

Having determined the region of high and low wall thickness, a protective tape 12, such as a neoprene or other elastomer tape, is placed over the inner circumference of the tube with the length of the tape extending the length of the tube. Such conventionally would cover about one-third to one-half the inner circumference of the tube. The tape is placed over the region of low wall thickness.

Having placed the tape the internal diameter of the tube is blasted with an abrasive, such as silicon carbide particles. This has generally the effect of removing material in the region which hasbeen shaded in FIG. 1. The length of time that the blasting takes place, and the particle size used in the blasting, is determined by the amount of material that it is desired to remove.

With an eccentricity in the starting tube or tube hollow of 20 percent of wall thickness, and a wall thickness is 0.350 inch, the tube has a maximum thickness in the high wall region of 0.420 inch, and: a minimum thickness in the low wall thickness region of 0.280 inch. Abrading might be continued under these circumstances, for a time sufficient to remove about 0.070 inch of material from the uncovered region. With the tape covering half of the inner circumference of the tube, this will leave a tube with a wall thickness at the high wall region a of 0.350 inch, a thickness at the region indicated at 10c (which is midway between the high and low wall thickness regions) of 0.280 inch, and a thickness at the region of minimum wall thickness of 0.280 inch.

Such blasting and removal of material introduces a slight ovality to the outline of the tube. This may be removed by working the tube, as by passing such through a tube reducer which reduces the area of the wall in the tube through reduction of its diameter and reduction of wall thickness. For instance, the tube or tube hollow above described may be reduced to a tube having an CD. of about 0.5 inch and a wall thickness of 0.050 inch, by passing such through a Mannesmann- McKay tube reducer in multiple passes, with approximately 50 percent area reduction in the wall thereof taking place in each pass.

Explaining how the process may be carried out on a tube with removal of material from the outer periphery of the tube, and referring to FIG. 2, here the tube is shown at 12, the zone of high wall thickness at 12a, and the region of low wall thickness at 12b. When removing material on the outer circumference of the tube, there is greater control over where the abrading action takes place. Blasting, for instance, may be directed against certain regions of the tube with other regions avoided, so that there is selective removal of material without actually providing a protective covering over any specific region of the tube. In any event, shown in FIG. 2 is a covering 14 applied to the region of low wall thickness. Material that is removed with the blasting is in that region which has been shaded in FIG. 2.

As another variation in the procedure it will be noted that in FIG. 2 material has been removed in a nonuniform manner, with most material removed in the region of greatest wall thickness, and a lesser amount of material in regions of lesser wall thickness. This is done by blasting the uncovered regions using a head that directs the particles during blasting, and by blasting for a longer time period the regions of greater wall thickness.

While certain embodiments of this invention have been described herein obviously changes and variations are possible without departing from the invention. It is desired to cover all such modifications as would be apparent to one skilled in the art.

It is claimed and desired to secure by Letters Patent: 1. A method of correcting eccentricity in the circumferential surfaces bounding a tube wall comprising determining high and low wall thickness regions in the tube, removing material from the region of high wall thickness, and working the tube to remove ovality in the cross section of the tube introduced by the removal of the material whereby roundness is returned to the tube. 2. A method of correcting eccentricity in the circumferential surfaces bounding a tube wall comprising determining high and low wall thickness regions in t e tube, app ymg a protective covering of one of the tubes circumferential surfaces on the low wall thickness region of the tube while leaving unprotected remaining wall regions of such one surface,

removing the material from the tube wall where such wall regions are unprotected, and

after removal of the covering working the tube to remove ovality in the cross section of the tube introduced by the material removal and to restore roundness thereto.

3. A method of preparing from a tube hollow having eccentric inner and outer circumferences tubing of reduced diameter and wall thickness with correction of such eccentricity comprising determining high and low wall thickness regions in the tube hollow,

applying a protective covering on one of the tubes circumferential surfaces over the low wall thickness region thereof while leaving unprotected the high wall thickness region,

abrading material from the tube wall from the unprotected high wall thickness region,

removing the protective covering,

and passing the tube hollow as so prepared through a tube reducer to reduce the wall thickness and diameter thereof and at the same time to remove ovality introduced by the abrading of the material from the tube wall. 

1. A method of correcting eccentricity in the circumferential surfaces bounding a tube wall comprising determining high and low wall thickness regions in the tube, removing material from the region of high wall thickness, and working the tube to remove ovality in the cross section of the tube introduced by the removal of the material whereby roundness is returned to the tube.
 2. A method of correcting eccentricity in the circumferential surfaces bounding a tube wall comprising determining high and low wall thickness regions in the tube, applying a protective covering of one of the tubes circumferential surfaces on the low wall thickness region of the tube while leaving unprotected remaining wall regions of such one surface, removing the material from the tube wall where such wall regions are unprotected, and after removal of the covering working the tube to remove ovality in the cross section of the tube introduced by the material removal and to restore roundness thereto.
 3. A method of preparing from a tube hollow having eccentric inner and outer circumferences tubing of reduced diameter and wall thickness with correction of such eccentricity comprising determining high and low wall thickness regions in the tube hollow, applying a protective covering on one of the tubes circumferential surfaces over the low wall thickness region thereof while leaving unprotected the high wall thickness region, abrading material from the tube wall from the unprotected high wall thickness region, removing the protective covering, and passing the tube hollow as so prepared through a tube reducer to reduce the wall thickness and diameter thereof and at the same time to remove ovality introduced by the abrading of the material from the tube wall. 